Another Heater Question (I searched & couldn't find the solution)

Quarterwave · Dec 18, 2004

Hi all,

Like many other XJ owners, with the onset of winter I've discovered that my heater doesn't heat to well when I need it to. So, after looking around this site, I found a link to someone that had posted what I need to do to flush out the heater core, which I thought was a job that I could do with my average handyman skills - however, I just have some specific questions that weren't covered in the article that I hope someone can answer....

1) Which two hoses am I mean't to pry off ? The ones located on top of each other which are mounted on the engine bay side of the firewall, or the same hoses but at the location right next to the rocker cover, where a few hoses all meet into 1 central connector ? If it is the ones on the firewall, how difficult are they to prize off ? As I got the clamp off the top hose, but the hose wasn't budging....

2) What size pliers (or type of tool if it's a specific one) do I need to prize off the circlip that clamps the heater send and return lines onto their nozzles ? As my average sized pliers get no where near the width needed to get a hold of the clips on the hoses in my 93'.

3) Does the HVAC need to be set to the heat setting ? Does the climate control need to be slid to the max. hot setting as well ?

4) Should I do it with the engine cold or should I run the engine for a bit with the heater on (possibly to loosen up the gunk inside the heater core?) ?

5) How and where do I fill up the heater core once it has been flushed ? Is Prestone radiator fluid ok to use or should I just use distilled water ?

Sorry for all the questions folks, but I'm currently living in an apartment complex and don't have access to my usual facilities or tools, so any pre-warnings might help me avoid making a HUGE mess in my parking lot !

Again, thx for all the assistance in advance.

B Rgds,
Quarterwave

5-90 · Dec 18, 2004

Usually, flushing the heater core can be flushed while you are doing the radiator - just run the engine and run the heater to "full hot" while you're doing it. I think you'll need to manualy apply vacuum to the heater control valve to force it open, but I can't swear to it at the moment. Why? As long as you're flushing, you might as well get it all.

Flushing just the heater core is possible, but I don't really see the reason (since you have to open the cooling system to get the job done anyhow - your heater just uses waste engine heat from the cooling system.)

You'll refill with 50/50 antifreeze and distilled/RO water (distilled or reverse osmosis filtered) just like the rest of the cooling system.

As far as the best place to pull hoses, I'd have to look. I've got "closed system" XJ's, and I've not gotten a good look at an "open system" recently, so anything I can give you here would be just a guess. Still, I'd go for the "full system" flush just to make sure I got everything - but that's just me. Bear in mind that a full flush should be done about every two years - when you change coolant anyhow...

5-90

w_howey · Dec 19, 2004

I actually just did this on my wife's 90. Now it is the 'early' closed system, not quite the same as your 93 but close enough I hope I can answer the questions.

First you can flush the just the heater core, with out moving the heat selector, on the early ones there is a valve in the engine bay that controls water flow to the coolant.

The two hoses you need to remove are the ones going thru the firewall to the heater core. You should be able to follow them from the water pump to where they go thru the firewall. If it was mine I would replace those spring clips with hose clamps, but that is a personal preference. I used a short screwdriver and slid the blade inside the edge of the hose around the core pipe, until it broke loose just a little. Then a twist the hoses instead of trying to pull, and off they come.

It doesn't matter wether the engine is cold or warm, I did it warm, just because I had to drive to a warm garage. (15 degree day).

When your are blasting the water into the core, it will remain in the core after you are done. I lost no more than an ounce or two of coolant when I removed the hoses. I just added a bit to the pressure bottle.

It will make a bit of a mess in your driveway/parking lot. But no more so than washing the XJ does. The only anti-freeze mixture dumped was the couple of ounces out of the hoses and whatever was in the core. I washed it all down the drain into the septic system, to make sure no toxic coolant was left out.

Quarterwave said:
Hi all,

Like many other XJ owners, with the onset of winter I've discovered that my heater doesn't heat to well when I need it to. So, after looking around this site, I found a link to someone that had posted what I need to do to flush out the heater core, which I thought was a job that I could do with my average handyman skills - however, I just have some specific questions that weren't covered in the article that I hope someone can answer....

1) Which two hoses am I mean't to pry off ? The ones located on top of each other which are mounted on the engine bay side of the firewall, or the same hoses but at the location right next to the rocker cover, where a few hoses all meet into 1 central connector ? If it is the ones on the firewall, how difficult are they to prize off ? As I got the clamp off the top hose, but the hose wasn't budging....

2) What size pliers (or type of tool if it's a specific one) do I need to prize off the circlip that clamps the heater send and return lines onto their nozzles ? As my average sized pliers get no where near the width needed to get a hold of the clips on the hoses in my 93'.

3) Does the HVAC need to be set to the heat setting ? Does the climate control need to be slid to the max. hot setting as well ?

4) Should I do it with the engine cold or should I run the engine for a bit with the heater on (possibly to loosen up the gunk inside the heater core?) ?

5) How and where do I fill up the heater core once it has been flushed ? Is Prestone radiator fluid ok to use or should I just use distilled water ?

Sorry for all the questions folks, but I'm currently living in an apartment complex and don't have access to my usual facilities or tools, so any pre-warnings might help me avoid making a HUGE mess in my parking lot !

Again, thx for all the assistance in advance.

B Rgds,
Quarterwave

Another Heater Question (I searched & couldn't find the solution)

Quarterwave

NAXJA Forum User

5-90

NAXJA Forum User

w_howey

NAXJA Forum User

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